1,4-Butanediol can be derived from succinic acid, maleic anhydride and other four-carbon organic species, but such methods are not economically attractive. Another method of producing 1,4-butanediol is by the reaction of formaldehyde and acetylene to form 1,4-butynediol as an intermediate, which is subsequently hydrogenated to the desired 1,4-butanediol product.
Other investigators have endeavored to convert acrolein into 1,4-butanediol by subjecting acrolein to hydroformylation conditions, the objective being the formation of succinaldehyde as an intermediate product. The results have been unsatisfactory since the main conversion product recovered from acrolein under hydroformylation conditions is propionaldehyde.
Other efforts to produce 1,4-butanediol have involved hydroformylation of allyl alcohol to yield 4-hydroxybutanal as an intermediate which is subsequently hydrogenated to 1,4-butanediol. The liquid phase hydroformylation of allyl alcohol in the presence of hydroformylation catalysts such as cobalt carbonyl produces significant quantities of propanal, propanol and 2-methyl-3-hydroxypropanal as by-products, in addition to the desired 4-hydroxybutanal.
In United States Patent Office Defensive Publication No. 904,021 (Nov. 21, 1972) there is disclosed an improved hydroformylation process for converting unsaturated alcohols into diols. In one embodiment the Publication process involves the hydroformylation of allyl alcohol with rhodium-phosphine complex catalyst to produce a reaction mixture which is subsequently hydrogenated to yield 63 percent 1,4-butanediol and 25 percent 2-methylpropanediol, based on the weight of allyl alcohol charged.
U.S. Pat. No. 4,017,550 describes a method for the manufacture of 1,4-butanediol by hydroformylation of cyclic acetals of acrolein to a 3-formylpropionaldehyde acetal intermediate, and then hydrogenation of the acetal intermediate. U.S. Pat. No. 4,024,197 describes a similar procedure for production of 1,4-butanediol.
U.S. Pat. No. 4,039,592 describes a method of butanediol production which involves (1) reacting propylene and a mixture of methyl acetate, water, acetic acid and methanol with oxygen in the vapor phase in the presence of a Group VIII noble metal catalyst to form allyl acetate, (2) converting the allyl acetate under hydroformylation conditions to a mixture containing monoacetate ester of 1,4-butanediol and 1,2-butanediol, and (3) de-esterifying the mixture under methanolysis conditions to yield the corresponding butanediols.
Tetrahydrofuran is another important organic commodity. It finds application as a versatile solvent medium and as an intermediate for the production of resins and other commercial products such as butyrolactone and succinic acid.
Tetrahydrofuran can be produced by catalytic hydrogenation of maleic anhydride or furan, as is described in patent literature such as U.S. Pat. Nos. 2,772,293; 2,846,449; 3,021,342; and references cited therein.
It is well known that tetrahydrofuran can be produced by a series of reactions starting with the reaction of aqueous formaldehyde and acetylene in the presence of a cuprous acetylide complex to form butynediol. An alkaline material such as the carbonate, bicarbonate or hydroxide of an alkali or alkaline earth metal is commonly added to this reaction to control pH. This alkaline material generally reacts with the formic acid generated in this reaction to form the metal formate. The product of this reaction is then passed to a hydrogenation zone where the butynediol is converted to 1,4-butanediol. The 1,4-butanediol is then converted to tetrahydrofuran employing about 10 percent sulfuric acid. This reaction is conducted under temperature conditions which permit recovery of tetrahydrofuran and water overhead from the reactor. The reaction medium in the reactor typically contains about 50-60 percent unconverted 1,4-butanediol, about 10 percent acid, about 10 percent water, and about 25 percent combined tars and salts. The build-up of tars and salts in the reactor is an undesirable characteristic of this type of process.
There is a need for new and improved commercial processes for the large volume production of both 1,4-butanediol and tetrahydrofuran. The development of such processes is under active investigation.
Accordingly, it is an object of the present invention to provide a new and efficient method for producing 1,4-butanediol.
It is another object of this invention to provide a new and efficient method for producing tetrahydrofuran.
It is a further object of the present invention to provide an economically feasible process for converting acrolein into 1,4-butanediol or tetrahydrofuran on a commercial scale.
Other objects and advantages shall become apparent from the accompanying description and examples.